Among compounds having pyridonecarboxylic acid as a basic skeleton, many are known to be useful as synthetic antibacterial agents because they have superior antibacterial action and a broad antibacterial spectrum. Inter alia, norfloxacin (JP-A 141286/1978), enoxacin (JP-A 31042/1980), ofloxacin (JP-A 46986/1982), ciprofloxacin (JP-A 76667/1983), tosufloxacin (JP-A 228479/1985), etc. are widely used in clinical treatment as an infectious disease remedy.
These compounds, however, are still unsatisfactory in antibacterial activity, enteral absorption, metabolic stability and side effect, especially phototoxicity and cytotoxicity.